It is (used as, and can be used as) a trick, which needs guidelines. If the coders involved are not willing to change interface behavior to follow convention/standards, then insofar ideally/pragmatically requiring/necessitating an (even just tooltip er alertbox style) interface/documentation change/addendum.
Normally in a "Version Control" system, the "expected behavior" is that One (1) Commit means One (1) Edit.
So first, some basic history (because not a single person here so far has mentioned they're aware or know the feature etymology/lineage, and I am being very patient as you can read).
Let me cite Stackexchange Co-Founder Spolsky theirself talking about Version Control, if being founder that maybe helps:
In 2010, software development author Joel Spolsky described
distributed version control systems as "possibly the biggest advance
in software development technology in the [past] ten years".4 https://en.wikipedia.org/wiki/Distributed_version_control (https://en.wikipedia.org/w/index.php?title=Distributed_version_control&oldid=955777812) quoting https://www.joelonsoftware.com/2010/03/17/distributed-version-control-is-here-to-stay-baby/ / https://web.archive.org/web/*/https://www.joelonsoftware.com/2010/03/17/distributed-version-control-is-here-to-stay-baby/
Know that, the way Joel set Edit Summary to work is mostly faithfully like a DVCS Commit Message (that would seem to be the/their intent and motive according to their just-quoted speaking, notably whilst albeit I am being openly attacked for asking about/using the/their word association), faithful to Git/Hg basically, with one strikingly officially undocumented change in behavior(!).
Knowing that, I am learning now how to adjust to the lack of documentation specifying the unusual/custom site program behavior, a rather suspicious user interface behavior for a programmer-centric site, which is not following the standard/convention used in other major/popular/Git/Hg Version Control systems (as much touted by our good leader Spolsky as being important to speak about).
I suggest: A tooltip or alertbox saying "You have 5 minutes in the current edit." would explain the actual behavior. Also, given the founding/foundational programming community here, maybe even homage to the fact succinctly/properly documenting it's setup to work exactly (in many if not most respects, with exact respect, even formally standardizable degrees of respect) like Git (and politely explaining the differential interface behavior), would Be Nice to the User.
That said, otherwise, maybe the current formal/informal advice, summarized from responses here, is:
Attack the user for thinking it works like a Commit Message and
Tell them "Do not edit so much with the text editor." and
"Interrogate them again [from another account] about saying Commit Message." and
Say "You're supposed to wait, even though it does not tell you." and
"Do not write/edit at that speed, just change speed." (...even though the question has been asked ad nauseum before, implying the interface has an issue??)? That is not being a nice interface.
The words "Grace Period" (as suggested by others as terminology) are not anywhere so we're forcing users to guess. I had to pull teeth and have my teeth pulled to learn the ~~bug~~ feature was even called/"termed" a "Grace Period" semi-in/formally. I had to ask the question here to know the bug was a feature called a Grace Period, on a site deeply prided for writing (user-centric... or what did "Superuser.com" mean?) documentation.
"You have 1 minute in current Edit Summary." would be nice. A static/dynamic counter, or at least a static message explaining it's, um, unique, behavior. (If somebody I mean someapp/someappy started just setting their own time for things and not expressing their behavior in English words first, I would be and am startled. That kind of "unique behavior" is not acceptable coming from a leader like Spolsky who is a programmer role model in being a faithful and evangelical Git Advocate, and that kind of "unique behavior" is not acceptable for a user interface.)
If the feature is a not a trick then why not explain to the user, and be nice interface?
"You have 20 seconds (Grade Period) in current Edit Summary." would be nice. Some warning, indication, advice, words while editing (and properly labeled at /revisions, for documental researchers who need viable timestamps, and who might perhaps reasonably think the site written by DVCS advocate Joel Spolsky would follow Git protocols) explaining the interface behavior in English would be nice.